In an electric arc furnace method being one of iron-making process, electric arc furnace dust is generated as industrial waste containing a zinc oxide component of about 1.5% to 2.0% of an amount of steelmaking, at the time of dissolution smelting of scrap. It has been said that twenty million tons of electric arc furnace dust is generated in the world and 500,000 tons of electric arc furnace dust is generated in Japan. A part of the electric arc furnace dust is further reduced in a reduction furnace and recycled as an iron-making raw material or a cement extender. Exhaust gas generated from the reduction furnace contains secondary dust (crude zinc oxide) in which zinc oxide is condensed.
Most of iron scrap is generated from discarded electric appliance or discarded vehicles. A surface for painting of the discarded electric appliance or discarded vehicle has been galvanized. The scrap contains paint, plastic, oil, and the like. Therefore, the electric arc furnace dust also contains harmful organic matter such as chlorides and dioxins, in addition to heavy metals such as zinc and lead. Meanwhile, the electric arc furnace dust contains about 20% to 30% iron and 20% to 30% zinc. Therefore, the electric arc furnace dust is very useful as resources.
Currently, crude zinc oxide produced from the electric arc furnace dust by various recycling techniques becomes a raw material for dry or wet zinc smelting. Main recycling technique is Wells furnace method, and other than this, a plasma method, an electric melting reduction method, an MF furnace method, a rotating bed furnace method, and the like can be mentioned.
Under such circumstances, Patent Document 1 relates to a zinc recovery method, and discloses a metal zinc recovery method from electric arc furnace dust containing zinc oxide generated from an iron scrap refining furnace or the like of the electric arc furnace method. Specifically, Patent Document 1 discloses mixing and kneading electric arc furnace dust or secondary dust with metal iron-containing powder, a reducing agent, a binding agent, and water, and thereafter, molding and further firing the mixture in a reduction furnace. With this configuration, in Patent Document 1, zinc oxide in the electric arc furnace dust or in the secondary dust is recovered as metal zinc vapor.